1. Field of the Invention
The present invention relates to an ink-jet printer and an ink tank for use in the inkjet printer, wherein the ink tank includes a foam for absorbing and holding ink.
2. Related Art
There is a related art foam-type ink tank used for an ink-jet printer. The foam-type ink tank has a foam containing portion for containing a foam which is used for absorbing and holding ink, an ink outlet that communicates with the foam containing portion, and ports communicating with the atmosphere for opening the foam containing portion into the atmosphere. When ink is sucked under the discharge pressure of an ink-jet head, air corresponding to the sucked amount of ink is caused to flow into the foam containing portion.
In the case of such a foam-type ink tank, a mechanism for detecting the presence or absence of ink in the ink tank in which ink is directly stored, for example, an optical sensor utilizing a prism reflective surface that returns light to the original reflective surface in the absence of ink, or a detection mechanism using a sensor utilizing a change in impedance originating from the presence or absence of ink across a pair of electrodes cannot be directly used to detect the presence or absence of ink.
Consequently, an ink end has heretofore been detected as the result of calculation of the used amount of ink according to the number of dots of ink discharged from the ink-jet head and the sucked amount of ink by an ink pump for sucking ink from the ink-jet head.
Incidentally, a condition in which ink in the ink tank has almost run out is generally called a xe2x80x98real endxe2x80x99 and a condition in which the remaining ink in the ink tank has decreased to a predetermined amount or smaller is also generally called a xe2x80x98near end.xe2x80x99 However, the xe2x80x98ink endxe2x80x99 used in this specification includes both of these conditions unless otherwise specified.
The method of detecting the ink end by detecting the running-out of ink by calculating the used amount of ink and the like has the following problems. Since the discharged amount of ink from the ink-jet head and the sucked amount of ink by means of the ink pump undergo wide variation, the used amount of ink that has been calculated according to these quantities also shows a variation far greater than that of the amount of ink actually used. Therefore, a great margin is usually set in order to settle the ink end. Consequently, a greater amount of ink may be left at a point of time when the ink end is detected, whereby ink may often be wasted.
It is therefore an object of the invention made in view of the foregoing problems to propose a foam-type ink tank wherein an ink end is made detectable precisely at a point of time substantially where no remaining ink exists therein.
Further, it is an object of the invention to propose an ink-jet printer having an ink-end detecting mechanism for detecting an ink end in such a novel foam-type ink tank.
In order to solve the foregoing problems, an ink tank according to the invention comprises: a foam for absorbing and holding ink; a foam containing chamber for containing the foam; a vent port communicating with the foam containing chamber, the vent port allowing atmospheric air to enter the foam containing chambers; an ink outlet for taking out ink from the foam containing chamber; and an ink chamber for detecting a remaining amount of ink, the ink chamber being disposed between the foam containing chamber and the ink outlet, the ink chamber operable to receive ink and bubbles from the foam containing chamber and supply only the ink to the ink outlet while preventing the bubbles from entering to the ink outlet.
According to the invention, the ink chamber is formed between the foam containing chamber and the ink outlet and when the remaining amount of ink in the foam containing chamber is running short, bubbles are allowed to enter the ink chamber from the foam containing chamber each time ink is supplied from the ink outlet. When the ink in the foam containing chamber runs out, the remaining amount of ink in the ink tank substantially becomes equal to the amount of ink left in the ink chamber. Therefore, an ink end can precisely be detected at a point of time where the remaining amount of ink substantially runs out by detecting the ink end in the ink tank according to the remaining amount of ink in the ink chamber while at the same time, the capacity of the ink chamber is made sufficiently small.
Although the above condition may be regarded as a real end so as to quickly halt the printing process, the printing process may continue by treating that condition as a near end as follows. That is, an amount of ink to be used thereafter is calculated after the ink end (near end) is detected when the condition is regarded as the near end and the real end can be decided when the calculated value reaches an amount equivalent to the capacity of the ink chamber. Even in this case, as only ink liquid is detected in the ink chamber, the remaining amount of ink is precisely detectable and the used amount of ink up to the real end is also calculable, so that waste of ink is reduced.
The ink tank has a projected portion projecting from a bottom wall of the ink chamber; and a communicating port formed at a front end of the projected portion, the communicating port communicating with the ink outlet.
In this case, as the ink outlet can be disposed near the base of the ink chamber, it is possible to make the ink tank compact, while an increase in its height is restrained.
To ensure that useless bubbles are retarded from entering the ink chamber and the ink passage, it is preferable to provide a first filter dividing the foam containing chamber and the ink chamber, the first filter formed of a first porous material which allows bubbles in the foam containing chamber to pass therethrough by an ink suction force acting on the ink outlet, and a second filter provided on the communicating port, the second filter formed of a second porous material having a pore diameter smaller than the pore diameter of the first porous material.
In this case, in order to supply the ink gathered in a position lower than the position in which the second filter is mounted in the ink chamber, the second filter is formed with an absorbing material portion for sucking up ink, the absorbing material portion being extended to the bottom wall of the ink chamber.
An absorbing material for sucking up ink may be disposed as another member different from the second filter, the absorbing material being extended from the communicating port to the bottom wall of the ink chamber.
A prism is preferably provided on one of walls of the ink chamber, wherein the prism reflects light received at the prism when the ink fails to contact the prism, and refracts the light into the ink chamber when the ink contacts the prism.
The remaining amount of ink is made detectable by forming two interface surfaces, each disposed facing at an oblique angle to one another, and each extending from the vicinity of a bottom wall of the ink chamber to the vicinity of an upper wall of the ink chamber. In this case, the setting of the value of the remaining amount of ink is made freely variable by making variable the optical sensor position for detecting the prism.
An ink tank according to the invention comprises: a foam for absorbing and holding ink; a foam containing chamber for containing the foam; a vent port communicating with the foam containing chamber, the vent port allowing atmospheric air to enter the foam containing chamber; an ink outlet for taking out ink from the foam containing chamber; an ink chamber for detecting the remaining amount of ink, the ink chamber being disposed between the foam containing chamber and the ink outlet, the ink chamber operable to receive ink and bubbles from the foam containing chamber and supply only the ink to the ink outlet while preventing the bubbles from entering to the ink outlet; a projected portion projecting from a bottom wall of the ink chamber; a communicating port formed at a front end of the projected portion, the communicating port communicating with the ink outlet; and a cap member for covering the projected portion, wherein
a gap for sucking up ink is formed between the projected portion and the cap member, the gap being extended from the communicating port to the bottom wall of the ink chamber.
When the ink absorbing material portion and the ink absorbing material are employed, as ink is sucked up by their capillary action, although there is an upper limit to an amount of ink to be sucked up. When the used amount of ink is large, for example, it is feared that the amount of ink sucked up by the capillary action may fail to catch up with what is actually required. In a case where the gap for sucking up ink is formed by using the cap member, a greater amount of ink can be sucked up in comparison with a case where the ink absorbing member or the ink absorbing material is employed by properly setting the width of the gap.
In order that useless bubbles are retarded from entering the ink chamber and the ink passage, it is preferable to provide the first filter dividing the foam containing chamber and the ink chamber, the first filter formed of a first porous material which allows bubbles in the foam containing chamber to pass therethrough by ink suction force acting on the ink outlet; and the second filter provided on the communicating port, the second filter formed of a second porous material having a pore diameter smaller than the pore diameter of the first porous material.
Provision of a projection for use in forming the gap for sucking up ink on the outer face of the projected portion and/or the inner face of the cap member makes formable a gap having proper width only by mounting the cap member.
The projection is preferably made to function as a projection for positioning the cap member with respect to the projected portion.
The cap member is such that a communicating section which communicates with the gap for sucking up ink is formed between an open edge face of the cap and the bottom wall of the ink chamber facing the open edge face thereof.
The open edge face of the cap preferably has a plurality of projections for use in forming the communicating portion, whereby the communicating portion is automatically formed when the cap is mounted on the projected portion.
In order to detect the amount of ink in the ink chamber according to the invention, it is desirable to provide a prism on one of walls of the ink chamber, wherein the prism reflects light received at the prism when the ink fails to contact the prism, and refracts the light into the ink chamber when the ink contacts the prism. Moreover, the remaining amount of ink is made detectable by forming the reflective surfaces of the prism, which are longer than are wide, in the depth direction of the ink chamber. In this case, the setting of the value of the remaining amount of ink is made freely variable by making variable the optical sensor position for detecting the prism.
A valve body capable of blocking the ink outlet and a spring member for pressing the valve body against the ink outlet are disposed between the communicating port and the ink outlet.
An ink-jet printer comprises: an ink-jet head for discharging ink,
an ink tank for ejecting ink to be supplied to the ink-jet head,
the ink tank further comprising:
a foam for absorbing and holding ink;
a foam containing chamber for containing the foam;
a vent port communicating with the foam containing chamber, the vent hole allowing atmospheric air to enter the foam containing chamber;
an ink outlet for taking out ink from the foam containing chamber;
an ink chamber for detecting the remaining amount of ink, the ink chamber being disposed between the foam containing chamber and the ink outlet, the ink chamber operable to receive ink and bubbles from the foam containing chamber and supply only the ink to the ink outlet while preventing the bubbles from entering to the ink outlet;
a prism having two interface surfaces provided on one of walls of the ink chamber, wherein the prism reflects light received at the prism when the ink fails to contact the prism, and refracts the light into the ink chamber when the ink contacts the prism, and
an ink-end detecting mechanism having a light emitting element and a light receiving element capable of receiving the light emitted from the light emitting element and also reflected from the two interface surfaces, wherein the presence or absence of ink in the ink tank is detected according to the remaining amount of ink in the ink chamber by the amount of light reflected from the prism.
With the arrangement above, as only ink liquid is detected in the ink chamber, the remaining amount of ink is precisely detectable and the used amount of ink up to the real end is also calculable, so that waste of ink is reduced.
In the ink-jet printer,
the ink tank includes:
a projected portion projecting from a bottom wall of the ink chamber; a communicating port formed at a front end of the projected portion, the communicating port communicating with the ink outlet; and
a cap member for covering the projected portion, wherein a gap for sucking up ink is formed between the projected portion and the cap member, the gap being extended from the communicating port to the bottom wall of the ink chamber.
With the arrangement above, as the ink outlet can be disposed near the base of the ink chamber, it is possible to make the ink tank compact while an increase in its height is restrained.
Moreover, a greater amount of ink can be supplied to the ink-jet head and simultaneously ink in the ink chamber can also be sucked up without waste of ink.